Add "paid at the door" ticket type to the Add Ticket modal.

Door walk-ins were only expressible as an unpaid ticket, which left the
cash out of revenue. The new type records the cash payment as paid and
makes every field optional, since a walk-in often gives no details:
a blank name is logged as "Walk-in", and a confirmation email only goes
out when an email is entered.

Door tickets reuse paymentStatus 'paid' (the column enum is capped at
paid/unpaid/comp) so badges and revenue totals pick them up with no
migration; the cash payment row is referenced "Paid at door" to keep
them distinguishable from emailed manual tickets.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/src/app/admin/events/[id]/_modals/EventModals.tsx

@@ -133,6 +133,16 @@ export function EventModals(props: EventModalsProps) {
               <p className="text-xs text-gray-500">Send confirmation email with QR ticket</p>
             </div>
           </button>
+          <button
+            onClick={() => { openAddTicket('door'); setShowAddTicketSheet(false); }}
+            className="w-full text-left px-4 py-3 rounded-btn text-sm hover:bg-gray-50 min-h-[44px] flex items-center gap-3"
+          >
+            <BanknotesIcon className="w-5 h-5 text-gray-500" />
+            <div>
+              <p className="font-medium">Paid at Door</p>
+              <p className="text-xs text-gray-500">Cash taken at the door, all fields optional</p>
+            </div>
+          </button>
           <button
             onClick={() => { openAddTicket('unpaid'); setShowAddTicketSheet(false); }}
             className="w-full text-left px-4 py-3 rounded-btn text-sm hover:bg-gray-50 min-h-[44px] flex items-center gap-3"